Optical energy which is produced by medical lasers is often delivered to a target tissue through the use of an optical fiber or flexible hollow waveguide. A wide variety of medical lasers with appropriate delivery systems are known and used for wide spectrum of treatments, including kidney stone or other stone disintegration, tissue ablation, and tissue coagulation, the way of example only. However, optical fibers and waveguides tend to be fragile and requires some degree of the mechanical support. This usually involves the placement of a polymeric, Teflon or other suitable material jacket covering and surrounding the optical fiber to provide such support.
Moreover, an optical fiber or waveguide consists of a concentric core element surrounded by one or more layers of cladding materials. In some cases, the core element may be a silica core or simply a hollow waveguide. The cladding material in a hollow waveguide may be silver or other internal coating while, in the case of an optical fiber, such cladding material may be a transparent solid material. A polymeric jacket may have an appropriate optical characteristic to serve not only as a protection for the cladding element but also serve as a secondary cladding material in addition to its mechanical support purposes.
During treatment, in which laser energy is passed through an optical fiber or waveguide's proximal end, the laser beam energy will exit from the distal tip of for example, the optical fiber. This distal tip will tend to become eroded during laser treatment due to the intensity of the laser's power. This is because in medical treatment such as ablation treatments or treatments in which the laser is used to disintegrate or break up for example kidney stones, the higher level of energies and fluence which are delivered through the optical fiber and the interference of tissue or stone fragments tend to cause erosion and disintegration of the fiber tip. This tip erosion is known to affect mainly the fiber core, the cladding materials, and, as mentioned, the fiber tip. Due to the materials and structure of the jacketing material there is less proportionate erosion of the jacketing materials.
During operation, as the distal tip of the fiber erodes and diminishes in length, the jacket itself tends not to erode, as mentioned above, at the same rate. FIGS. 1A and 1B illustrate this phenomena. As can be seen in FIG. 1A, whereas the fiber tip 1 has eroded there is little erosion in the jacket material 2. Since, in a number of procedures, it is necessary or at least desirable to place the fiber tip against the bodily material that is to be ablated, it can be seen in FIG. 1A that the remaining jacket material prevents such contact. In addition, as can be seen in FIG. 1B, the jacket material 4, due in part to heating from the laser beam energy, may become jagged and may further make it difficult to contact the bodily material to be ablated. Another disadvantage is that the field of vision may be limited. Finally, when the jacketing material those fragment and separate from the remainder of the optical fiber and jacket combination, fragments which have separated may be large enough to interrupt the optical path of the laser beam, further complicating the medical procedure.
Thus, what is needed is an optical fiber jacket which eliminates the problems described above yet which provides an orderly destruction, erosion or disintegration of the optical fiber jacket more in synchronization with the erosion of the optical fiber tip itself.